Daydreams of the tropical paradise of Hawai'i rarely include snow in the imagery, but nearly every year, a beautiful white blanket covers the highest peaks in the state for at least a few days. However, systematic observations of snowfall and the snow cover dimensions on Mauna Kea and Mauna Loa are practically nonexistent. A group of climate modelers led by Chunxi Zhang from the International Pacific Research Center (IPRC) at the University of Hawai'i at Manoa used satellite images to quantify recent snow cover distributions patterns. They developed a regional climate model to simulate the present-day snowfalls and then to project future Hawaiian snowfalls. Their results indicate that the two volcano summits are typically snow-covered at least 20 days each winter, on average, but that the snow cover will nearly disappear by the end of the century.
To evaluate the current situation, Zhang and his colleagues examined surface composition data retrieved from satellite imagery of Hawai'i Island from 2000 to 2015 to construct a daily index of snow cover. They used this data compilation to evaluate the quality of their regional atmospheric climate model, based on global climate projections that included several scenarios of anticipated climate change. Zhang then ran simulations representative of the end of the 21st century, assuming a moderate business-as-usual scenario for greenhouse gas emissions projections, to establish how long Hawai'i might enjoy its occasional glimpses of white-topped mountains.
"We recognized that Hawaiian snow has an aesthetic and recreational value, as well as a cultural significance, for residents and visitors," explained Zhang. "So, we decided to examine just what the implications of future climate change would be for future snowfall in Hawai'i." Unfortunately, the projections suggest that future average winter snowfall will be ten times less than present day amounts, virtually erasing all snow cover.
The findings were not a total surprise, with future projections showing that even with moderate climate warming, air temperatures over the higher altitudes increase even more than at sea level, and that, on average, fewer winter storm systems will impact the state. However, the group's new method for establishing the current snow cover on these Hawaiian mountains provides another avenue for monitoring the progression of climate change in the region. Ultimately, this study also illustrates the benefits of the recent trend in model downscaling, highlighting the regional and local effects of global climate change.

It is well-established in the scientific community that increases in atmospheric CO2 levels result in global warming, but the magnitude of the effect may vary depending on average global temperature. A new study, published this week in Science Advances and led by Tobias Friedrich from the International Pacific Research Center (IPRC) at the University of Hawai?i at Mānoa (UHM), concludes that warm climates are more sensitive to changes in CO2 levels than cold climates.
Increasing atmospheric CO2 concentrations cause an imbalance in the Earth's heat budget: more heat is retained than expelled, which in turn generates global surface warming. Climate sensitivity is a term used to describe the amount of warming expected to result after an increase in the concentration of CO2. This number is traditionally calculated using complex computer models of the climate system, but despite decades of progress, the number is still subject to uncertainty.
The new study, which included scientists from the University of Washington, the University at Albany, and the Potsdam Institute for Climate Impact Research, took a different approach in calculating climate sensitivity: using data from the history of Earth. The researchers examined various reconstructions of past temperatures and CO2 levels to determine how the climate system has responded to previous changes in its energy balance.
"The first step was to reconstruct the history of global mean temperatures for the last 784,000 years, using combined data from marine sediment cores, ice cores, and computer simulations covering the last eight glacial cycles," said Friedrich, a post-doctoral researcher at IPRC.
The second step involved calculating the Earth's energy balance for this time period, using estimates of greenhouse gas concentrations extracted from air bubbles in ice cores, and incorporating astronomical factors, known as Milankovitch Cycles, that effect the planetary heat budget.
"Our results imply that the Earth's sensitivity to variations in atmospheric CO2 increases as the climate warms," explained Friedrich. "Currently, our planet is in a warm phase -- an interglacial period -- and the associated increased climate sensitivity needs to be taken into account for future projections of warming induced by human activities."
Using these estimates based on Earth's paleoclimate sensitivity, the authors computed the warming over the next 85 years that could result from a human-induced, business-as-usual greenhouse gas emission scenario. The researchers project that by the year 2100, global temperatures will rise 5.9°C (~10.5°F) above pre-industrial values. This magnitude of warming overlaps with the upper range of estimates presented by the Intergovernmental Panel on Climate Change (IPCC).
"Our study also allows us to put our 21st century temperatures into the context of Earth's history. Paleoclimate data can actually teach us a lot about our future," said Axel Timmermann, co-author of the study and professor at UHM.
The results of the study demonstrate that unabated human-induced greenhouse gas emissions are likely to push Earth's climate out of the envelope of temperature conditions that have prevailed for the last 784,000 years.
"The only way out is to reduce greenhouse gas emissions as soon as possible," concluded Friedrich.

It is well-established in the scientific community that increases in atmospheric CO levels result in global warming, but the magnitude of the effect may vary depending on average global temperature. A new study, published this week in Science Advances and led by Tobias Friedrich from the International Pacific Research Center (IPRC) at the University of Hawai?i at Mānoa (UHM), concludes that warm climates are more sensitive to changes in CO levels than cold climates.
Increasing atmospheric CO concentrations cause an imbalance in Earth's heat budget: more heat is retained than expelled, which in turn generates global surface warming. Climate sensitivity is a term used to describe the amount of warming expected to result after an increase in the concentration of CO . This number is traditionally calculated using complex computer models of the climate system, but despite decades of progress, the number is still subject to uncertainty.
The new study, which included scientists from the University of Washington, the University at Albany, and the Potsdam Institute for Climate Impact Research, took a different approach in calculating climate sensitivity: using data from the history of Earth. The researchers examined various reconstructions of past temperatures and CO levels to determine how the climate system has responded to previous changes in its energy balance.
"The first step was to reconstruct the history of global mean temperatures for the last 784,000 years, using combined data from marine sediment cores, ice cores, and computer simulations covering the last eight glacial cycles," said Friedrich, a post-doctoral researcher at IPRC.
The second step involved calculating Earth's energy balance for this time period, using estimates of greenhouse gas concentrations extracted from air bubbles in ice cores, and incorporating astronomical factors, known as Milankovitch Cycles, that effect the planetary heat budget.
"Our results imply that Earth's sensitivity to variations in atmospheric CO increases as the climate warms," explained Friedrich. "Currently, our planet is in a warm phase -- an interglacial period -- and the associated increased climate sensitivity needs to be taken into account for future projections of warming induced by human activities."
Using these estimates based on Earth's paleoclimate sensitivity, the authors computed the warming over the next 85 years that could result from a human-induced, business-as-usual greenhouse gas emission scenario. The researchers project that by the year 2100, global temperatures will rise 5.9°C (~10.5°F) above pre-industrial values. This magnitude of warming overlaps with the upper range of estimates presented by the Intergovernmental Panel on Climate Change (IPCC).
"Our study also allows us to put our 21st century temperatures into the context of Earth's history. Paleoclimate data can actually teach us a lot about our future," said Axel Timmermann, co-author of the study and professor at UHM.
The results of the study demonstrate that unabated human-induced greenhouse gas emissions are likely to push Earth's climate out of the envelope of temperature conditions that have prevailed for the last 784,000 years.
"The only way out is to reduce greenhouse gas emissions as soon as possible," concluded Friedrich.

The Asia-Pacific Economic Cooperation (APEC) Climate Symposium 2013 was held with the theme of regional cooperation on drought prediction science for disaster preparedness and management. Gusti Muhammad Hatta, the Indonesian minister for research and technology, opened the symposium, noting the importance of the event in strengthening drought preparedness in order to contribute to the APEC mission of sustainable economic growth and prosperity in the Asia-Pacific region. In his keynote address, Donald Wilhite, professor at the University of Nebraska-Lincoln and founder of the National Drought Mitigation Center, presented a state-of-the-art system for monitoring drought conditions in the United States. The second keynote address, by Andi Eka Sakya of the Indonesia Agency for Meteorology, Climatology, and Geophysics (BMKG), focused on a potential drought monitoring information system for Indonesia. He introduced the geographical and climatological conditions of Indonesia and explained other existing information systems produced by BMKG. The conference presentations described the extent of existing research and scientific understanding of the processes and mechanisms that control rainfall and other variables relevant to drought in different areas.